Power plant frame structure having air-cooling means for turbine rotors and exhaust frame struts



April 1952 B o. BUCKLAND ETAL 91,399

POWER PLANT FRAME STRUCTURE HAVING AIR'COOLING MEANS FOR TURBINE ROTORSAND EXHAUST FRAME STRUTS Original Filed June 11, 1947 2 SHEETS--SHEET 1Inventors: Bruce QBuckland, Alan Howard, by W Their Attorney April 1, 152 B. o. BUCKLAND ET AL 2,591,399

POWER PLANT FRAME STRUCTURE HAVING AIR-COOLING MEANS FOR TURBINE ROTORSAND EXHAUST FRAME STRUTS Inventors: Bruce OBuckland, Alan Howard, b W

Their Attor'n ey Patented Apr. 1, 1952 POWER PLANT FRAME STRUCTUREHAVING AIR-COOLING MEANS FOR TURBINE R- TORS AND EXHAUST FRAME STRUTSBruce 0. Buckland and Alan Howard, Schenectady, N. Y., assignors toGencral Electric Company, a orp ra ion of N w York.

Original application June 11, 1947, Serial No. 754,002. Divided and thisapplication January 20, 1951, Serial No. 206,966

C aim 1 This invention relates to gas turbine powerplants, particularlyto a novel frame structure for the turbine of such a powerplant, havingspecial means for cooling the frame components so as to facilitatemaintenance of correct alignment of the respective bearings and minimumclearances at the shaft packings and turbine bucket tips.

The present application is a division of a copending application, serialNo. 754,002, filed June 11, 1947, in the names of Alan Howard, ChesterS. Rice, and Bruce 0. Buckland, and assigned to the same assignee as thepresent application.

In the design of gas turbine powerplants, a major consideration is theprovision of arrangements for permitting free differential thermalexpansion between relative parts without producing undesirabledeformation of the rotor or material alteration of the clearancesbetween the rotor and variou stationary parts. Because of the extremelyhigh temperatures to which certain parts must necessarily be subjected,it is necessary to use special high temperature resisting materials,such as various stainless steels. These generally have a coefficient ofexpansion in the neighborhood of twice that of ordinary mild carbonsteel, with the result that utilization ofsuch materials magnifies theproblems resulting from differential thermal expansion. Furthermore, ina powerplant designed for applications where the load must ,befrequently and materially altered, as for instance in marineinstallations and locomotives, it is found that differential thermalexpansion problems are intensified still further by differences inthesize and mass of various related parts, and differences in theresistance of the heat flow paths to them from the source of heat, withaccompanying differences in the rate of change of dimension whentemperatures change "rapid- 13'. The resulting differential thermalexpansions introduce special problems when the rotor of the machine isof sufficient length and mass as to require a plurality of axiallyspaced bearings. In such a machine, it is absolutely necessary, in orderto avoid vibration troubles and abnormal bearing loads and shaftstresses, that the frame structure be arranged so differential thermalexpansion will not have the effect of impairing the bearing alignment.The problems become even more difficult when it is necessary to providea bearing at the exhaust side of the turbine rotor; so that the membersfor supporting this bearing must go either through or around the turbineexhaust casing.

Accordingly, the object of the present invention (Cl. GD-39.32)

is to provide an improved frame structure for a high temperature gasturbine having special means for cooling the frame components so as toprevent bearing misalignment due to differential thermal expansionbetween the respective bearins supporting c mponents- Another object isto provide a turbine structure in which t e hot as s ar co ined in aPassa formed partly by segmental pieces of stainless steel. so arran das to transmit a. minimu of heat to the cooled supporting structure sothat the supporting structure may be fabricated of low carbon steels.Thus, the use of costly high temp rature st el alloys is mi imi d.

A further object is to provide gas turbine structure in which the hotcomponents, that is, the comparatively thin sheet metal walls whichdefine the hot gas, passages, are arranged so as to be free to flexunder the influence of temperature changes, such flexing preventing thetransmission of excessive deforming forces to the frame memhere.

A still further object is to provide a cooled turbine frame structure ofthe type described in which spent cooling fluid is used to cool andpressurize certain shaft seals and the space adjacent the turbine rotorso as to prevent the entrance of hot motive fluid into that space.

Other objects and advantages will become apparent from the followingdescription taken in connection with the accompanying drawings, in whichFig. 1 is a perspective view of the combustion and turbine sections of agas turbine powerplant incorporating the invention with one combustorremoved; Fig. 2 isa detailed view in partial ection showing the turbineframe structure to which the present invention particularlyrelates; andFig. 3 is a partial sectional view at the plane 3.3 in Fig. 2, showing adetail of the cooled frame structure.

Generally, the present invention is practiced by providing a pluralityof main frame rings surrounding the respective bucket-wheels of theturbine rotor and connected together in axially spaced relation bycylindrical casing sections, with a system of axially and radiallyextending struts extending from the respective frame rings so as to fixthese rings in space relative to the bearing housing members. One set ofstruts passes between respective pair of the circumferentially spacedcylindrical type combustion chambers, while the other set of strutspasses through the annular turbine exhaust casing. special cooling meansinclude a fan rotor carried on theturbine shaft and adapted to drawcooling air through 3 holes in the main frame rings and through coolingshrouds surrounding each of the struts which passes through the turbineexhaust casing 50 that the high, and at, times circumferentially uneven,temperature of the exhaust fluid will not affect adversely the lengthand shape of the struts.

Referring now more particularly to Fig. 1, the powerplant includes acombustion system indicated generally at I, a turbine assembly at 2, andan exhaust casing at 3.

As will be seen in Fig. 1, the combustion system comprises a pluralityof circumferentially spaced similar combustion chambers or combustors 4,each of generally cylindrical configuration and spaced circumferentiallyaround the axis of the powerplant. Only one of the combustors is shownin section (Fig. 2), and the structural details thereof will not bedescribed herein since they comprise the subject matter of a copendingapplication, Serial No. 62,333, filed November 27, 1948, in'the name ofBruce 0. Buckland, now Patent No. 2,547,619, and assigned to the sameassignee as the present application. Asfwill be seen in Fig. 2, thecombustors 4 are spaced circumferentially around and radially away froma substantially cylindrical frame member 1. At its right-hand end, theframe cylinder member 1 carries a journal bearing 8. Welded to thecylindrical frame member 7 adjacent the journal bearing 8 is a radiallyextending annular plate 9, which has a circumferential row-of openingsaround each of which is welded one end of a short cylinder ll having atthe other end a'fiange 12 adapted to support the turbine end of theouter combustor casing. To the outer circumference of the transverseplate 9 is welded an axially extending cylinder l3, which entirelysurrounds the transition end of the combustion system. At its right-handend, cylinder I3 is welded to a continuous main frame ring is, to whichis secured the main frame ring i5, for instance by a plurality ofthreaded fastenings IS, in a manner which will be more apparent fromFig. 3.

While the transverse plate 9 and the axially extending cylinder l3 helpto support the frame ring I4 from the cylinder 1, a principal portion ofthe support between these members is provided by a'plurality ofcircumferentially spaced diagonally extending ribs or struts ll, therebeing one such strut between each pair of adjacent combustors. At theleft-hand radially inner end, each strut l! is welded to the left-handend of the frame cylinder 1 in a manner which will be understood from acomparison of Figs. 1 and 2. At an intermediate portion, each strut I1is provided with an inwardly extending portion Ila (see Fig. 1) weldedto the transverse plate 9 and an'axially extending portion l'lb weldedto the outer circumference of the frame cylinder member 1. 'At itsradially outer end, each strut I! is provided with an axially extendingportion l'lc welded to the outer surface of frame cylinder [3 and theadjacent radial face of frame ring it. Thus, it will be seen that themembers 1, l1, 9, I 3 and [4 form an extremely rigid integral frameserving to hold the journal bearing 8 in fixed space relation to themain frame ring 15.

Secured to the mainring 15 by bolts I8 is an interstage turbine casingindicated generally at I8 in Fig. 2. This casing is not an integralannular member, but is formed in two halves divided along a verticalplane through the axis of the turbine and secured together by aplurality of threaded fastenings 19. 'At its downstream side,

interstage casing I8 is provided with a second radially extending fiangeI8?) secured by bolts to a second integral main frame ring 2!. Bolted tothe exterior face of ring 21, adjacent the inner periphery thereof, isan exhaust casing fabricated of comparatively thin flexible sheets andhaving a somewhat conical external wall 22, a cylindrical inner wall 23,and a discharge casing 24 witha flanged outlet opening 25. The dischargecasing is provided with a flat end wall plate 24a which extends upwardlyto somewhat above the center-line of the powerplant and then flaresoutwardly, as indicated at 24b in Fig. 2. Plate 24a is normal to theaxis of the powerplant, and the central portion thereof is connectedwith the outwardly flaring portion 24b by a central dished portion 240.

Projecting diagonally across the annular passage defined by exhaustcasing walls 22, 23 are a plurality of circumferentially spaced,radially and axially extending struts or ribs 26. When there are sixcombustors, it is convenient to use six of these struts, the same numberas there are of the struts ll. At its radially outer end, each strut 26is secured, as by bolting or welding, to the main frame ring 2!. Eachstrut projects through an opening 22a in the outer exhaust casing wall22 and through a second opening 23a in the inner exhaust casing wall 23.Surrounding each strut 26 in spaced relation thereto is a cooling airshroud 21, which projects through the respective openings 22a, 23a andis welded to the peripheries thereof. These shrouds 21 form a coolingair path surrounding each strut 26, as described more particularlyhereinafter, and also serve to support the inner exhaust casing wall 23from the outer exhaust casing wall 22,

, Welded to the shrouds 21 and arranged within the turbine exhaustpassage are a plurality of guide vanes 28 adapted to direct the turbinedischarge fluid smoothly outward into the exhaust casing 24. Theoutermost vane 28a extends all the way to the vicinity of the main framering 2| and is sealed thereto by any suitable means. Thus, it will beseen that member 2811 forms the outer wall of the passage for theturbine discharge fluid. The innermost guide vane 28b is secured to theouter circumference of the cylin drical wall 23. The walls 23 and 24aare provided with openings at 29, which openings form a discharge portfor cooling air, as described hereinafter. As will be apparent from Fig.2, the turning vane 28b forms one wall of this cooling air outlet. r 7

At the radially inner ends, the struts 26 are welded to an integralconical frame member 30. At its outer end, adjacent the last-stageturbine bucket-wheel, frame member 30 is providedwith an inwardlyextending flange portion 3| which is connected by a convoluted annularflexible member 32 to the adjacent edge of the inner casing wall 23. Atits exterior end, the conical frame member 30 is provided with a heavyflange member 33, to which is secured the housing 34 of the exhaust endjournal bearing 35. Bearing housing 34 is for convenience split into twohalves along a horizontal plane and secured together by the threadedfastenings 36. The lower half of casing 34 is provided with a projectingboss 3'! which forms a socket for receiving a ball member 38 secured toan end support pedestalss. It will be understood that the ballsupportlarrangement 3T, 38, 39 provides one fixed support point for thepowerplant. The end of bearing housing 34 is closed by a cap member 50,which'may. alsobe formed in two halves bolted together at the horizontalcenter-line. Also secured to the end ring 33 of frame member is alabyrinthcasing 4| having labyrinth seal members 4|a adapted tocooperate with portions of the turbine rotor for preventing the flow ofoil vapors from bearing 35 to the left into the cooling air passagesdescribed hereinafter.

It is desired to direct attention to the fact that this entire framestructure is designed throughout so that the load-supporting and bearingaligning members are maintained at a comparatively low temperature sothat ordinary, comparatively inexpensive, easily worked and readilyavailable steel alloys may be used for the frame and casing members. Theuse of mild steel for the principal frame members results in the furthervery great advantage that differential thermal expansion is reduced byreason of its lower coefficient of thermal expansion, as compared withhigh temperature alloys such as the stainless steels.

Having described in some detail the casing and frame structure for theturbine, it will be observed that the rotor comprises a first-stageturbine bucket-wheel, indicated generally at 42, having' a hub portionformed integral with a shaft extension 43 and a first radially extendingweb portion 44, to which is welded a circumferential rim portion 45.This rim portion carries a circumferential row of blades or buckets 46,which may be secured to the rim 4-5 by any suitable means, such asdove-tails, welding, etc. The buckets shown are of the shroudless oropenended type. This bucket-wheel construction is the so-calledcomposite bucket-wheel more fully described in Patent 2,432,315, issuedto Alan Howard on December 9, 1947, and assigned to the same assignee asthe present application.

The second-stage turbine bucket-wheel, indicated generally at 41 is alsoof this composite construction and has a circumferential row ofshroudless buckets 48. Formed integral with the bucket-wheel 41 is anaxially extending shaft'end portion 49, which serves a number ofpurposes. The end of shaft portion 49 is supported in the journalbearing 35, at the exterior side of which it is provided with a couplingflange 5D, to which is bolted an internally splined coupling member 51.The input shaft 52 of a suitable load device (not shown) extends throughthe bearing end cap and is provided with splines 53 engaging thecooperating splines of the coupling member 5|. Further details of theturbine rotor construction are not material to the understanding of thepresent invention, and therefore will not be described in further detailhere, such details being covered by the copending application of Bruce0. Buckland and Chester S. Rice, Serial No. 208,961, filed on February1, 1951 and assigned to the same assignee as the present application.

The nozzle ring assembly for directing hot motive fluid into thefirst-stage bucket-wheel 46 is indicated generally at 54, and theinterstage diaphragm assembly defining the nozzle ring for directingmotive fluid into the second-stage buckets 48 is indicated generally at55, in Fig. 2.

The details of these assemblies are not described particularly hereinsince they are covered by the copending application of Alan Howard,Serial No. 107,306, filed on July 28, 1949, and assigned to the sameassignee as the present application. It is of interest to note here thatthe portions of these assemblies which define the walls of the hightemperature motive fluid ,fl-ow path are flexibly supported or mountedso as to be free to shift relative to the main supporting frame members,the latter being maintained cool so as to retain their shape anddimensions.

The special arrangements for cooling the casing -and frame structurewill now be described.

The main frame rings [4, I5, Isa, [81), and 2| are provided withcooperating holes. Ma, [5a, I80, I801, and Ma. These holes define axialcooling air passages spaced rather closely circumferentially around themain frame rings, as may be seen in Fig. 3.

It will be seen in Fig. 2 that the cylindrical frame member l5 and theinterstage casing 18 cooperate with an enclosing air cooling shroud 56to define a cooling air passage having an annular inlet at 51. Thiscylindrical cooling shroud 56 closely surrounds the main frame rings I4,l5, 18a, 18b, and 2| and has a right-hand end portion 58 sea-linglyengaging the exhaust casing 24.

As will also be seen in Fig. 2, the inner cylindrical wall 23 of theexhaust casing, in combination with the flexible ring 32, the innerconical frame member 30 and annular baille 59 coopcrate to define anannular space $5 communieating with the cooling air passages definedbetween the cooling shrouds 27 and the support struts 2,5. These airpassages are in communication by way of the openings in the exhaustcasing with the annular space contained within the cooling air shroud56. Cooling air is drawn into the shroud inlet 53 through the coolingair holes in the frame rings and through the cooling shrouds 21 into thechamber 66 by a cooling fan described more particularly hereinafter.

At the left-hand end of frame member 30 in Fig. ,2, the ring 31 carriesa casing 5i which supports a labyrinth packing member 62 an: definescooling and sealing air passages 53 which furnish cooling fluid to amid-point of the labyrinth seal 62a. Bolted to an intermediate portionof frame member 30 is a curved annular shroud 64, which has an inneredge portion forming a close clearance with a radially projecting flange65 on the turbine rotor end portion 49. Also secured to an intermediateportion of frame member 30 is a second ring member 66 provided with aplurality of circumferentially spaced axially extending guide blades 61.Spaced around the frame member 38 are a plurality of openings ,63 whichprovide access from the annular chamber 60 to the cooling air fan inletdefined 'by shroud 64, ring 56, and the guide blades 6]. Secured to theturbine rotor portion 25 :by any suitable means are a plurality ofcircumferentially spaced axial flow fan blades 69 having tip portionsforming a small radial clearance with the inner circumference of shroudring .56 and adapted to draw air in through the openings 160, past theguide blades 81, and to discharge this cooling air into an annulardischarge passage 15 defined by an inwardly projecting wall 1] formedintegral with the end ring 33. Adiacent the end ring 35, frame member 35is provided with a circumferential row of spaced openings 12, throughone of which projects the inlet end of an impact tube 1.3, which isarranged to catch some of the air discharged from fan blades .69 and todeliver it under pressure to thechamber 53 of the labyrinth seal cas- Iing 6.1. This portion of the air is divided at the labyrinth seal 62a,part of it flowing to the .left as indicated by the arrow 1114, so as to.cool

the exhaust side of bucket-wheel 55. This wheel cooling air isdischarged into the main turbine fiow path as indicated by the arrow 15.The remaining openings 12 and the frame member 38 serve as dischargeports for the rest of the cooling air from fan 65?. To preventrecirculation of cooling air from the discharge ports 12 back into theinlet ports 68, the conical baffle 59 is secured from the frame memberto the inner port rings l4, l5, Ida, l8b, 2|, etc., thence through thestrut cooling shrouds 21 into the space), thence through ports 68 to thefan inlet guide vanes 61. The cooling air is discharged through .ports12 and the opening 29 into the exhaust casing, where it mixes with theturbine discharge fluid.

While it is possible to use high pressure air from the compressor forperforming all the turbine wheel cooling functions, it is to be notedthat this high pressure air is "expensive in terms of the power takenfrom the main rotor to supply it. An improvement in over-all thermalefiiciency is obtained if the comparatively low pressure air for coolingand sealing the discharge side of the last-stage bucket-wheel isfurnished by a separate axial flow fan such as the blower 69.

While the air discharged into the spaces adjacent the bucket-wheelserves to cool the turbine rotor, it should also be noted that this airmay serve another important function, as follows. In high temperatureturbines of the type described, there is at least some tendency for hotmotive fluid to leak from the main flow path into the clearance spacesdefined between the bucketwheels and adjacent casing structure. Thishigh temperature leakage flow may cause serious overheating; but, byintroducing cooling air in the manner described above, the spaceadjacent the bucket-wheel is pressurized with comparatively cooler air,thereby resisting the tendency for hot fluid to leak into these spaces.

From the above description of the exhaust casing and the main frameworkwith its cooling system, it will be apparent that the exhaust casing issupported at a radially outer circumference adjacent the last-stagebucket-wheel,

where it is secured to the frame ring 2|, being also supported at aradially inner circumference axially spaced from the second-stagebucketwheel, where it is supported by bafile 59 from the main framemember 39. Frame member 30 is rigidly supported from the frame ring 2|by the air-cooled struts 26, which framework re mains of substantiallyconstant dimensions during operation, while the exhaust casing must befree to readily expand and contract relative to this cool framework whensubjected to the high temperature exhaust fluid. Therefore, the entireexhaust casing, comprising walls 22, 23, 24, 24a, 24b, 240, isfabricated of relatively thin sheet steel which will readily change.dimension and deflect as necessary to compensate for differentialthermal expansion between the exhaust casing and the cooled supportingframework. thereof. This arrangement, by which the-casing is carried bythe frame ring 2| and the inner frame member 30, readily permits suchdifferential' thermal expansion without disruptive stresses beingcreated in the casing or distortion produced in the, main framework.Thus, it will be seen that the flow path is formed by comparatively thinflexible sheets, which are free to heat and cool rapidly and to deflectreadily under the influence of differential expansion, while the mainload-carrying support members are kept cool and out of contact with thehot fluid, and thus free from distortion and other troubles incident tohigh temperature operation.

The construction of the main framework and its special cooling system asdescribed above insures that the principal load-carrying members willremain comparatively cool and, therefore, will not change dimensionsmaterially as operating temperatures vary in the hot parts carried bythe frame. Because the temperature of these load-carrying members(struts ll, rings l5, 2|, members 30, 26, etc.) is maintained at acomparatively low value, they may all be fabricated of ordinary mildsteel, which is cheap, easily obtainable, and readily worked and welded.This has the additional very great advantage of decreasing the changesin the dimensions of the main frame members as operating temperatureschange, by reason of the lower coefficient of expansion of mild steel,as compared with that of the available high temperature resistingmetals.

Those hot parts of the powerplant which do need to be fabricated of hightemperature stainless steels, for instance, the combustor liners, nozzleblades, interstage diaphragm blades, etc., are all supported from thecooled framework by means which permit free differential thermalexpansion therebetween.

In brief, throughout the design of this powerplant, the load-carryingfunction has been separated from the hot fluid conducting func-' tion,the former being performed by frame and easing members which are adaptedto remain sufliciently cool that they can be made of ordinarylow-itemperature metals, while the latter function is performed by partsmade of hightemperature metals flexibly supported from the cooler frameparts. This arrangement greatly simplifies the serious problems ofmaintaining proper bearing alignment and the clearances required betweenthe various rotor components and associated stator and easing members.

It will be apparent to those skilled in the art that, while a preferredform of this cooled turbine frame structure has been described herein,many of the details may be modified in various ways withoutv departingfrom the invention; and it is intended to cover by the appended claimsall such modifications as fall within the true scope of the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is: i

1. In a high temperature gas turbine powerplant, the combination of afirst substantially cylindrical frame member, first bearing meanssupported from said frame member adjacent one end thereof, a pluralityof circumferentially spaced combustors disposed around and supported inradially spaced relation from said frame member, a nozzle ring assembly,meanssuppOrting the nozzle ring coaxial with and radially spaced fromthe bearing end of said first'frame member, walls forming transitionducts for leading hot motive fluid from the combustorsto the nozzlering, a first main frame ring coaxial with and substantially in theplane of the nozzle ring, a plurality of circumierentially spaced strutseach having an inner end portion secured to the first frame member at alocation remote from said first hearing and extending diagonally outwardbetween adjacent combustors with an outer end portionsecured to thefirst main frame ring, an interstage turbine casing divided into atleast two portions along axial planes and secured together at saidplanes, said casing having an annular flange at either end including afirst flange secured to the first main frame ring, a second main framering secured to the second flange, a turbine exhaust casing locatedimmediately adjacent and secured to the second frame ring and forming anannular turbine discharge passage, a second axially extending framemember of substantially circular cross section arranged within theturbine exhaust casing, second bearing means secured to the exterior endof said second frame member, a plurality of circumferentially spacedstruts connected at one end to the second main frame ring and extendingaxially and radially inward through the turbine discharge passage andhaving inner end portions connected to said second frame member, acooling shroud surrounding each of the last-named struts and connectedat either end to the exhaust casing to define a cooling air passagesurrounding the strut, a turbine rotor supported in said first andsecond bearing means and having a first bucket-wheel locatedsubstantially in the plane of the first main frame ring with acircumferential row of buckets adapted to receive motive fiuid from thenozzle ring and a second bucket-wheel arran ed substantially in theplane of the second main frame ring and in series flow relation with thefirst wheel, said rotor having a portion forming a cooling blowerimpeller located within the second frame member, an external shroudextending from the exhaust casing and closely surrounding the first andsecond main frame rings, said shroud, frame rings, sec-- ond framemember, and exhaust casing defining passages whereby said blower drawscooling air, through the frame rings and strut cooling passages anddischarges spent cooling fluid into the exhaust casing.

2. In a high temperature powerplant having a turbine rotor with at leastone axial flow bucketwheel, the combination of first bearing means forthe inlet end of the rotor, a frame with means for supporting the inletend bearing; said frame including also a continuous main frame ringlocated substantially in the plane of the last-stage bucket-wheel, aturbine exhaust casing supported by said ring and defining an annulardischarge passage for the bucket-wheel, an axially extending framemember of substantially circular cross section arranged within theexhaust casing, second bearing means for the discharge end of the rotorsupported by the exterior end of said frame member, a plurality ofcircumferentially spaced struts connected at one end to the main framering and extending axially and radially inward through the turbinedischarge passage and having inner end portions connected to said framemember, a cooling shroud surrounding each of the struts and connected ateither end to the exhaust casing to define a cooling air passagesurrounding the strut, walls defining an annular cooling chambersurrounding the rotor at the downstream side of the bucket-wheel, meanson the turbine rotor forming a cooling blower impeller located withinsaid frame member, an external shroud extending from the exhaust casingand closely surrounding the main frame ring, said frame ring and framemember and exhaust casing defining passages whereby the blower drawscooling air through the frame ring and strut cooling passages anddischarges said cooling fluid into the exhaust casing, and conduit meansfor delivering a portion of the fluid discharged by the cooling blowerto said chamber for cooling the exhaust side of the bucket-wheel andpressurizing the space adjacent the bucket-wheel web to resist thecirculation of hot motive fluid therainto.

3. In a high temperature powerplant having a turbine rotor with at leastone axial flow bucketwheel, the combination of a frame with bearingmeans for supporting the respective end por tions of the rotor, saidframe including a continuous main frame ring coaxial with the rotor andlocated substantially in the plane of the laststage bucket-wheel, anexhaust casing supported by said ring and defining an annular dischargepassage for the bucket-wheel, an axially extending member ofsubstantially circular cross section arranged within the exhaust casingand having an exterior end portion adapted to support one of the rotorbearings, a plurality of circumferentially spaced struts connected atone end to the main frame ring and extending axially and radially inwardthrough the turbine discharge passage and having inner end portionsconnected to said axially extending member, walls defining a coolingshroud surrounding each of the struts, each of said shrouds beingconnected at either end to the exhaust casing and spaced from the strutto define a cooling air passage surrounding the strut, an annular membersurrounding the rotor within said axially extending member and spacedfrom the discharge side of the bucket-wheel to form a cooling air spacetherewith, labyrinth seal means carried by said annular member andforming close clearances with the rotor, means carried by the turbinerotor forming a cooling blower impeller located within said axiallyextending member and axially intermediate the cooling air chamher andthe end bearing, said frame ring, exhaust casing, and inner axiallyextending member defining passages whereby the blower draws cooling airin contact with the main frame ring and through the strut coolingpassages and discharges a portion of the cooling fluid into the exhaustcasing, and conduit means for delivering a second portion of the fluiddischarged by the cooling blower to an intermediate portion of saidlabyrinth seal whereby the seal member is cooled and cooling fluidescaping from the seal passes into said cooling chamber to cool thedischarge side of the bucket-wheel and pressurize said chamber to resistthe leakage of hot motive fluid thereinto.

4. In a high temperature turbine powerplant having a rotor with an axialflow bucket-wheel, the combination of a main frame including acontinuous ring member surrounding and substantially in the plane of thebucket-wheel, an axially extending frame member of circular crosssection arranged coaxial with the rotor and adjacent the discharge sideof the bucket-wheel, bearing means for the rotor carried by said framemember, an exhaust casing having a radially outer end portion adjacentthe bucketwheel secured to the main frame ring and a second radiallyinner end portion secured to the axially extending frame member at alocation remote from the bucket-wheel, the exhaust casing having wallsdefining an annular turbine discharge passage for the bucket-wheel andbeing fabricated of comparatively thin flexible sheetswhereby the casingis free to change its dimensions and deflect as necessary to permitdiiferential thermal expansion relative to the supporting frame, aplurality of circumferentially spaced struts each having a first endportion secured to the main frame ring and extending axially andradially inward through the turbine discharge passage and having asecond end portion secured to the axially extending frame member, Wallsdefining, a cooling shroud surrounding each of the struts and spacedtherefrom to form a cooling fluid passage, and means for circulating acooling fluid through said passages to maintain the support struts at acomparatively low temperature whereby changes in the dimensions of thesupporting frame during operation are minimized.

5. In a high temperature powerplant having a turbine rotor with at leastone axial fiow bucketwheel, the combination of first bearing means forthe inlet end of the rotor, a frame with means for supporting the inletend bearing, said frame including also a continuous main frame ringlocated substantially in the plane of the last stage bucket-wheel, aturbine exhaust casing supported by said ring and defining an annulardischarge passage for the bucket-wheel, an axially extending framemember of substantially circular cross section arranged within theexhaust casing, a second bearing means for the discharge end of therotor supported by the exterior end of said frame member, a plurality ofcircumferentially spaced struts connected at one end to the main framering and extending axially and radially inward through the turbinedischarge passage and having inner end portions connected to said framemember, a cooling shroud surrounding each of the struts and connected ateither end to the exhaust casing to define a cooling air passagesurrounding the struts, means on the turbine rotor forming a coolingblower impeller located within said frame member, an external shroudextending from the exhaust cas ing and closely surrounding the mainframe ring, said frame ring and frame member and exhaust casing definingpassages whereby the blower draws cooling air through the frame ring andstrut cooling passages and discharges said cooling fluid in the exhaustcasing.

BRUCE O. BUCKLAND. ALAN HOWARD.

No references cited.

